The present invention is directed to an ultraviolet (UV) treatment for aqueous liquids such as water or biological fluids.
There are many approaches to treating aqueous liquids. The approach taken depends upon a number of factors including the nature of the liquid, the object of the treatment, and the site of treatment, among other factors.
In the case of water to be used for human consumption, the object of treatment might be: to remove certain toxins, such as halogenated hydrocarbons or lead; to reduce the pathogenic content, e.g., render bacteria or viruses less virulent; or to remove components that detract from the taste or smell, but which are otherwise relatively harmless. The site of treatment might be a communal source such as a municipal water treatment plant, or it could be at the point of use, such as in the home.
The present invention involves the use of UV radiation in treatment of aqueous liquids. When the liquid is drinking water, for example, an object is to reduce its pathogenic content. It has been known for quite some time that UV light has bactericidal properties (U.S. Pat. No. 1,193,143, issued Aug. 1, 1916; U.S. Pat. No. 1,200,940, issued Oct. 10, 1916; United States). It is now understood that UV radiation can act to degrade genetic material of a microorganism, i.e., RNA and DNA, to render the microorganism unable to reproduce. This renders the population of microorganisms less virulent and possibly completely harmless to humans.
The use of UV radiation in treating biological fluids is known in a variety of contexts. Exemplary objectives include inactivation of viruses (U.S. Pat. No. 5,789,150, issued Aug. 4, 1998) and inhibition of aggregation of blood platelets (U.S. Pat. No. 5,591,457, issued Jan. 7, 1997). The treatment might involve a person""s own blood (international patent application published as WO/98/22164 on May 28, 1998), or the treatment might be in preparation of donated blood or a blood product for administration to another person.
The patent literature describes a large number of apparatuses and methods of UV treatment of aqueous liquids.
One early approach is described in the specification of U.S. Pat. No. 1,193,143, issued Aug. 1, 1916 to Henri et al. This document describes an apparatus in which a UV lamp is placed outside the liquid and the liquid is caused to flow through a trough. The lamp is provided with a reflector and the sides of the troughs and baffles are made of a reflecting material, in order to utilize the rays emitted from the lamp to their fullest possible extent. In all illustrated arrangements, the lamp is located over the liquid. The liquid is caused to pass and re-pass through the rays in several different ways. In two illustrated embodiments, the liquid is caused to move up and down between baffles. In a third illustrated embodiment, the trough takes the form of a zigzag tube arranged in a horizontal plane. In a fourth illustrated embodiment, the trough is of a spiral form and is arranged so that the liquid in its passage therealong is exposed at all parts to the influence of the UV light.
The specification of U.S. Pat. No. 1,200,940, issued Oct. 10, 1916, also to Henri et al., describes an apparatus in which the UV lamp is immersed in the treatment liquid in order to increase efficiency of exposure of the liquid to UV rays. The lamp is protected from contact with the lamp by a quartz window.
The specification of U.S. Pat. No. 1,367,000, issued Feb. 1, 1921 to Pole, describes another apparatus in which the UV lamp is immersed in the treatment liquid. Again, the lamp is shielded from contact with the liquid by a quartz window. In this case, the treatment liquid flows through a narrow channel defined by quartz plates, the channel being located near a UV lamp.
The specification of U.S. Pat. No. 1,473,095, issued Nov. 6, 1923, again to Henri et al., describes an apparatus in which the treatment liquid is passed through one or more compartments located adjacent a UV lamp. Each compartment has a quartz window to permit exposure of the liquid within each compartment to UV light.
The specification of U.S. Pat. No. 2,504,349, issued Apr. 18, 1950 to Prieto, describes a water purification apparatus having a tray which defines a tortuous path which is sloped for the water to travel therealong under the force of gravity. Troughs are defined by the tray to permit the water to travel in a comparatively shallow sheet from the inlet point to the point of discharge. UV lamps are mounted to overlie the troughs. The troughs are formed of a material having high reflecting and low absorption factors. The specification states that the tortuous path which the water takes and the slope of the troughs are such that sufficient time elapse between the delivery of the water to the troughs and its discharge therefrom to enable the UV light from the lamp to be completely effective in disposing of all of the bacteria therein. The angularity or slope of the troughs is such that the water will flow in a stream of substantial uniform depth with a minimum of turbulence throughout its tortuous travel over the tray. There may be a series of parallel (in plan) longitudinal troughs connected in series to each other, or there can be a single trough in the form of a gradually declining spiral. Each lamp is provided with a reflector (semi-circular or parabolic in cross-section) to increase exposure of treatment liquid to UV rays.
The specification of U.S. Pat. No. 4,102,645 describes a sterilization apparatus having a UV lamp located above the liquid being treated, there being a quartz window located between the treatment area and the lamp. An inlet conduit leading into the treatment area is provided with a venturi for introducing air into the liquid. The air is introduced so that an air pocket is maintained above the liquid in the treatment area to prevent direct contact of the liquid with the quartz window and thereby prevent the accumulation of mineral deposits thereon, which deposits would interfere with transmission of UV rays.
There are UV water purifiers which can be connected in-line to water systems. Examples of such purifiers are described in specifications of U.S. Pat. No. 4,968,437 (issued to Noll et al. on Nov. 6, 1990), Canadian Patent Application No. 2,119,543 (published on Sep. 23, 1994 in the names of Kuennen et al.), and Canadian Patent Application No. 2,132,929 (published on Mar. 27, 1996 in the name Szabo).
An example of a system for monitoring the intensity of UV radiation within the treatment chamber of a water purifier is described in the specification of U.S. Pat. No. 4,849,100, which issued to Papendrea on Jul. 18, 1989. The system is suitable for a portable, gravity system in which the UV lamp is housed in a quartz sleeve.
The specification of U.S. Pat. No. 5,039,402, which issued to Himelstein on Aug. 13, 1991, describes a water purifier incorporated into a household coffee maker.
The specification of U.S. Pat. No. 5,628,895, which issued to Zucholl on May 13, 1997, describes a UV water treatment system in which a UV lamp is located above a container of water.
The use of a laser beam has been suggested by Goudy, Jr., in the specification of U.S. Pat. No. 4,661,264, for disinfection of liquids, typically as part of a larger wastewater treatment facility. Water is passed through a laser beam light produced at a suitable UV wavelength, in one embodiment, the laser source is positioned out of contact with the fluid but with its beam filling the cross-section of the stream of fluid to treat the liquid. A sensor (photocell) is trained at the reflected laser beam and is responsive to the amount of light which is reflected back up toward the surface. The less the light, the greater the turbidity. The photoelectric cell is used to control the oscillator or potentiometer of the laser source and thereby to control the pulse rate of the laser in response to changes in turbidity. Other means for determining turbidity are described. Flow meters are provided which adjust the rate of pulsing of the laser, and therefore the intensity of the ultraviolet light, in relation to changes in flow. This reference also suggests that all interior surfaces of all containers of each embodiment described can advantageously be provided with reflective surfaces to reflect the laser beam and take advantage of the scattering effect which will necessarily result from any suspended particles.
A very recent UV water disinfector is described in the specification of U.S. Pat. No. 5,780,860, which issued to Gadgil et al. on Jul. 14, 1998. This approach involves an apparatus having a UV lamp positioned over the water treatment area, and a gravity driven water delivery system is described. The specification mentions that the use of reflectors which redirect UV light toward the feed water offers the advantage of a providing a higher net dosage of UV light to the feed water. Although the approach does not seem to require a thin sheet of water such as that described by Prieto, the specification emphasizes the need for laminar flow of water through the treatment chamber. To this end, a baffle wall is provided at the upstream end of the treatment chamber, the baffle wall having a plurality of spaced perforations to provide for the desired pattern of water flow into the treatment chamber. A reflective wall is provided just downstream of the baffle wall. As characterized in the patent specification, a very low energy UV lamp is all that is required to treat large amounts of water because of the flow design. This reference also teaches that transmittance decreases with increasing turbidity and dissolved salts. It is suggested to monitor turbidity by providing a small visual pattern, such as a square with black and white bars, at the end of an entry feed trough below the water mark. An observer then positions her eyes at the farthest rim of the trough, and observes the lines to determine if they are distinct. If the lines are not distinct, then the liquid is too turbid to be suitable for treatment. Treatment of other fluids is also described by Gadgil et al., for example, elimination of bacterial contaminates in fish culture systems and disinfection of biohazardous liquids such as serum used in producing vaccines to dangerous pathogens.
In one broad aspect, the present invention is based on the apparently heretofore unrecognized advantages that can ensue from disrupting the flow of a liquid moving at ambient pressure under the force of gravity as it is being treated with UV.
This first aspect of the present invention is thus a process for treating an aqueous liquid. The process includes: (1) passing the liquid by force of gravity through a treatment area, the liquid having an upper surface exposed to ambient pressure; (2) disrupting the flow of the liquid as it passes through the treatment area; and (3) exposing the upper surface of the liquid as the flow is disrupted to UV light. The step of disrupting the flow is carried out so as to direct lower portions of the liquid toward the surface of the liquid to bring such portions into more direct contact with the UV light than would otherwise be the case.
Preferably, the UV light is provided by one or more UV lamps. The range of wavelengths of UV light is understood by the skilled person. UV light having a wavelength of about 254 is known to have germicidal properties.
According to certain embodiments, it is preferred for the liquid to have an average depth of no more than about 3 cm when being treated with UV light. The average depth may also be limited to about 2 cm, about 1 cm, about 0.5 cm or 0.3 cm or less.
In a preferred approach, disrupting the flow of liquid involves passing the liquid under the force of gravity down a trough in the treatment area, the trough being shaped to provide physical barriers which purposefully obstruct the even flow of liquid flowing through the trough. The main purpose of the obstructions is to force portions of the liquid resident at the bottom of the trough upwardly toward the surface of the liquid. This brings a greater proportion of the contents of the liquid into close contact with the UV light rays and thus increases the effectiveness of the action of the UV light on the liquid.
Another aspect of the present invention is an apparatus for treating an aqueous liquid such as water with UV radiation. The apparatus includes a treatment chamber having an upwardly open trough. The trough defines a flow path for the liquid to flow under the force of gravity under ambient pressure. There is an ultraviolet lamp spaced from the flow path to preclude contact of the lamp with the liquid and located to permit exposure of a top surface of liquid in the trough to radiation emitted from the lamp. The trough has a floor which is shaped to disrupt laminar flow and/or to promote uneven flow of the liquid as it passes through the trough to direct lower portions of the liquid in contact with the floor of the trough toward the upper surface of the liquid. The disruption of the flow should be sufficient to mix the components of the liquid over the span of the flow path through the treatment area of the apparatus. The mixing can be as great that the liquid can be described as turbulent, at least as far this term applies to liquids flowing under the force of gravity.
The present invention has been found to be particularly useful in the area of counter top or portable appliances for treating drinking water within a few hours or just prior to consumption. The illustrated embodiment, described in detail below is one such appliance.
In another broad aspect, the present invention addresses problems associated with monitoring the effectiveness of a UV water treatment. A particular application of the present invention is in the area of household appliances for use in treating tap water for human consumption. Although this aspect of the invention is not limited to household appliances, an important consideration in this area is the fact that many users rarely, if ever, have the desire or will to directly test the output of a device, that is, to test a sample of treated water for content of undesirable substances. At the same time, a typical consumer desires to be reasonably confident that a given water treatment is producing the desired effect.
In one embodiment of this aspect, the invention is an apparatus for treating an aqueous liquid such as water with UV light. The apparatus includes a treatment chamber for the liquid, a UV lamp, and an upwardly open trough for receipt of the liquid in the treatment chamber. The trough has one or more surfaces oriented to define a flow path for the liquid to flow therethrough. The UV lamp is spaced from the flow path and located to permit exposure of a top surface of liquid in the trough to UV light emitted from the lamp so as to permit entry of the UV light into the liquid. The trough also includes reflective surfaces located to be submerged by liquid flowing through the trough and oriented to reflect light upwardly into the liquid. There are two sensors included as part of the apparatus. The first sensor is located and trained to receive UV light emitted from the lamp. The second sensor is located and trained to receive UV light reflected from reflective surface(s) submerged below the surface of the liquid. The apparatus also includes means for determining the intensity of UV light received by the first sensor relative to the intensity of UV light received by the second sensor so as to determine the effectiveness of the treatment.
The precise way in which effectiveness is determined is achievable in a variety of ways, the preferred ways known to the inventors being described below. The advantage of this arrangement is that for a given appliance, say one for treating tap water to ensure its potability, there is no need for a user to test the water being treated to ensure that the treatment is effective. Generally, a consumer appliance of this type would be equipped with a simple indicator that shows if the treatment is effective. An example of such an indicator is a green light emitting diode (LED) that would be turned on when the treatment is working properly. Thus, in a preferred aspect, the apparatus includes an indicator operably connected to the first sensor and to the second sensor to provide an indication of when the UV light received by the second indicator relative to the UV light received by first indicator is below a predetermined level. So long as the UV light received by the second indicator relative to the UV light received by first indicator is not below this predetermined level, the green LED would remain on. Additionally, another, say red LED, could be included to show that when the UV light received by the second indicator relative to the UV light received by the first indicator has fallen below the predetermined level, the red LED would light up, showing that the water being treated might not be safe to drink, and should therefore be discarded.
The apparatus can also include another indicator operably connected to the first sensor to provide an indication of when the UV light received by the first indicator is below a predetermined level. This indicator, say a red LED, would specifically show that the UV lamp of the apparatus is not functioning at the level needed to be certain that the treatment would be effective. This situation could arise when the machine has just been turned on and the lamp is not yet warmed up to the point where it is emitting sufficient UV light. It could also arise when the lamp is broken or worn down and needs to be replaced.
Additionally, the apparatus can include an indicator operably connected to the first sensor to provide an indication of when the UV light received by the first sensor is above a predetermined level. This could be a green LED.
In a specific embodiment, the first sensor is trained to receive UV light rays emitted directly from the lamp. That is, the first sensor is aimed directly at the lamp. A person skilled in the art could, if need be, arrange the components of the apparatus so that the sensor receives rays indirectly from the lamp, say by use of a mirror. As described in detail in connection with the preferred embodiment, an operational principle of this monitoring aspect of this invention is that the sensors receive UV rays from different parts of the treatment area. The first sensor receives rays from the light source, which rays have not been diminished in intensity by absorption by the liquid being treated. The second sensor is oriented to deliberately receive UV rays from the light source that have passed through the liquid being treated and that have been reflected from reflective surface(s) submerged beneath the liquid. It is comparing the intensity of these two types of rays received by the two sensors that the effectiveness of the treatment is determined.
The second sensor can be trained to receive light rays that form an angle of between 0xc2x0 and about 150xc2x0 with light rays emitted from the lamp. The angle might be between 0xc2x0 and about 120xc2x0, between about 45xc2x0 and about 120xc2x0, or between about 80xc2x0 and about 100xc2x0. In the disclosed embodiment, the angle is about 90xc2x0, but it might be possible to improve performance by changing this angle.
The apparatus can be a portable table top appliance, say about the size of a conventional drip coffee maker.
The greater the degree of reflectance from the reflective surfaces, the more effective the treatment. This is because the reflected rays make there way back into the liquid being treated and thus increase the dosage of the UV rays being applied to the liquid. This is more the case when the liquid itself is highly translucent. Preferably, the reflective surfaces reflect at least 25% of UV light emitted from the lamp in the absence of liquid; better yet, the reflective surfaces reflect at least 40% of UV light emitted from the lamp in the absence of liquid; better still, the reflective surfaces reflect at least 90% or even 95% or more of UV light emitted from the lamp in the absence of liquid.
Different ways of obtaining increased reflectivity are discussed in connection with preferred embodiments. Many types of surfaces, that might be initially thought to be suitable, are not inert to water or other aqueous liquids that are treatable according to the invention. Additionally, even if a surface that were perfectly reflective to UV light and entirely inert to the liquid being treated were found, the possibility still exists of the surface becoming dirty over time. This would lead to decreased UV reflectivity and the need to clean the surface. In the context of preferred aspects of this invention, this would become evident by the lighting up of a red LED when the intensity of UV light received by the second sensor relative to the intensity of UV light received by the first sensor is to determined to be too low. Alternatively, or additionally, a green LED, lit up to indicate proper operation of the apparatus, would go out under such circumstances.
An appliance is thus preferably arranged so that the reflective surfaces can be readily cleaned. In one example of the invention, the surfaces are part of a removable tray. The tray can be cleaned, if required, or replaced by a new tray.
If the apparatus is a portable counter top appliance, it preferably includes a liquid storage chamber located in an elevated location with respect to the treatment chamber. There is one or more apertures in a wall thereof, the apertures being in communication with the treatment chamber to permit, under the force of gravity, controlled flow of a said liquid from the storage chamber to a said trough of the treatment chamber. By controlled flow, is meant that there is a maximum rate at which it is possible for liquid to exit the storage chamber and enter the treatment chamber. In atable top appliance, only so much liquid can fit into the storage chamber and so it is possible for there to be only so much pressure exerted by the liquid, and this determines the maximum rate at which the liquid can enter the treatment chamber through the fixed hole(s).
To obtain maximum benefit of the purifying power of UV rays, one would additionally include a trough that defines a flow path for the liquid to flow under the force of gravity under ambient pressure where the trough includes a floor which is shaped to promote uneven flow of the liquid as it passes through the trough to direct lower portions of the liquid in contact therewith toward the surface of the liquid. The benefits of this aspect of the invention are described elsewhere.
In another broad aspect, the present invention is a process for treating an aqueous liquid in which the treatment process is monitored. The process includes passing the liquid through a treatment area to bring the liquid into contact with reflective walls submerged below an upper surface of the liquid, and exposing the upper surface of the liquid to light emitted from a UV light source such that UV light penetrates the liquid to strike the submerged reflective surfaces and to be reflected therefrom to emerge through the upper surface of the liquid. As these steps are being carried out, the process also involves determining the intensity of the UV light emitted from the light source, determining the intensity of UV light received by a UV light sensor trained to receive emergent light and determining whether the treatment has a predetermined effectiveness based on the intensity of the UV light emitted from the light source and the intensity of the UV light received by the sensor.
Preferably, the process includes determining the intensity of UV light received by the UV light sensor when the treatment area is empty in order to determine whether the surfaces are sufficiently reflective for the treatment to have the predetermined effectiveness. This acts as a check on the condition of the of the reflective surfaces.
The process can include determining whether the intensity of the UV light emitted from the light source is sufficient for the treatment to have the predetermined effectiveness. Again, in terms of an apparatus in which the process is being carried out, sufficient UV light from the source can be indicated by an activated green LED, for example.
The process can also include providing an indication of the presence of an unsafe operating condition when the intensity of light received by the UV light sensor when the treatment area is empty is below a predetermined level. This can be indicated by activation of a red LED.
The process can also include providing an indication of the presence of an unsafe operating condition when the intensity of light received by the UV light sensor when the treatment area is empty is below a predetermined level. This can be indicated by activation of a red LED.
The process can include providing an indication of the presence of an unsafe operating condition when the intensity of the UV light emitted from the light source is below a predetermined level. Again, this can also be indicated by activation of red LED.
The process can include providing an indication of the presence of an unsafe operating condition when the intensity of UV light received by the sensor relative to the UV light emitted from the light source is below a predetermined level. Again, this can be indicated by activation of a red LED.
The liquid treated in the process can be any one of several aqueous liquids. In the case of this aspect of the invention, where reflective surfaces are submerged below the liquid, translucent liquids are preferred to be treated. For example, lake water, or tap water that has been chlorinated.
In a preferred process, the treatment has the predetermined effectiveness based on the intensity of the UV light emitted from the light source and the intensity of the UV light received by the sensor when the UV light received by the sensor is above about 70% the intensity of the UV light emitted from the light source.
In a preferred process, the light source is a mercury lamp.
In a slightly different broad aspect, a process of the invention includes the steps of:
passing the liquid through a treatment area to bring the liquid into contact with reflective walls submerged below an upper surface of the liquid;
exposing the upper surface of the liquid to light emitted from a UV lamp such that UV light penetrates the liquid to strike the submerged reflective surfaces and to be reflected therefrom to emerge through the upper surface of the liquid;
determining the intensity of UV light received by a first UV light sensor trained to receive UV light emitted from the light source;
determining the intensity of UV light received by a second UV light sensor trained to receive light emerging from the liquid; and
determining whether the treatment is effective based on the intensity of the UV light received by the first sensor and the intensity of the UV light received by the second sensor.
The process can include determining the intensity of UV light received by the second UV light sensor when the treatment area is empty in order to determine whether the surfaces are sufficiently reflective for the treatment to have the predetermined effectiveness.
The process can include determining whether the intensity of the UV light received by the first UV light sensor is sufficient for the treatment to have the predetermined effectiveness.
The process can include providing an indication of the presence of an unsafe operating condition when the intensity of light received by the second UV light sensor when the treatment area is empty is below a predetermined level.
The process can include providing an indication of the presence of an unsafe operating condition when the intensity of the UV light received by the first UV sensor is below a predetermined level.
The process can include providing an indication of the presence of an unsafe operating condition when the intensity of UV light received by the second sensor relative to the intensity of the UV light received by the first sensor is below a predetermined level.
Other aspects of the invention are described in connection with the preferred embodiments and in the claims.